A motorized window treatment system may include a covering material wound onto a roller tube. The covering material may include a weighted hembar at a lower end of the covering material, such that the covering material extends vertically (e.g., hangs) in front of a window. Motorized window treatments may include a drive system that is coupled to the roller tube to provide for tube rotation, such that the lower end of the covering material can be raised and lowered (i.e., moved in a vertical direction) by rotating the roller tube. The drive system may include a motor having a drive shaft and a gear train that is operatively coupled to (e.g., in communication with) the drive shaft and roller tube such that actuation of the motor causes the roller tube to rotate. The motor may be a direct current (DC) motor powered by a DC power source or an alternating current (AC) motor powered by an AC power source.
The torque capability and efficiency of a DC motor may vary depending on the motor speed. While the particular values of motor speed, torque capability, and efficiency may vary for different DC motors, certain characteristics may be shared by most DC motors. For example, motor speed and motor torque capability may vary linearly, and inversely, throughout the entire range of motor speeds including very low speeds approaching zero. Motor efficiency may generally reach peak efficiency under light-duty conditions (e.g., relatively low torque capability at a motor speed greater than 50% of maximum motor speed). When a DC motor operates at a peak efficiency (e.g., at greater speeds), the motor may generate undesired noise. Manufactures may operate the motor at a slower speed and a lower efficiency, to reduce a noise level of the motor.